Phenotyping exertional breathlessness using cardiopulmonary cycle exercise testing in people with chronic airflow limitation.

Abstract

Background: Exertional breathlessness is a cardinal symptom of people with chronic airflow limitation (CAL) and can be evaluated using cardiopulmonary exercise testing (CPET).

Research question: Does abnormally high exertional breathlessness in relation to the rate of oxygen uptake (V'O₂) and minute ventilation (V'_E) indicate different underlying pathophysiological mechanisms and clinical characteristics in people with CAL?

Study design and methods: Analysis of people aged ≥40 years with CAL (post-bronchodilator FEV₁/FVC upper limit of normal) by V'O₂ alone, abnormal by both V'O₂ and V'_E (B-V'O₂+V'_E), or normal by both V'O₂ and V'_E (B-normal). Exercise physiological responses and clinical characteristics were compared between groups.

Results: We included 325 people (44% women) with CAL (FEV₁ 75.4±[standard deviation] 17.5%predicted). Compared with the B-normal group (n=237[73%]), the B-V'O₂ group (n=29 [9%]) had lower pulmonary diffusing capacity and greater exercise ventilatory inefficiency, whereas the B-V'O₂+V'_E group (n=50[15%]) had even worse lung function, dynamic critical inspiratory constraints, and exertional breathlessness along with greater symptom burden in daily life, lower physical activity, and worse health status.

Interpretation: Exertional breathlessness phenotyped in relation to V'O₂ and V'_E using normative reference equations enable multivariable analyses of underlying symptom mechanisms and associated clinical characteristics.